Question

decide whether these proposed lewis structures are reasonable.
proposed lewis structure is the proposed lewis structure reasonable?
h — c — c — h
yes.
no, it has the wrong number of valence electrons.
the correct number is: 10
no, it has the right number of valence electrons but doesnt satisfy the octet rule.
the symbols of the problem atoms are: *
n — o — cl :
yes.
no, it has the wrong number of valence electrons.
the correct number is:
no, it has the right number of valence electrons but doesnt satisfy the octet rule.
the symbols of the problem atoms are: *
h — c ≡ c :-
yes.
no, it has the wrong number of valence electrons.
the correct number is:
no, it has the right number of valence electrons but doesnt satisfy the octet rule.
the symbols of the problem atoms are: *

• if two or more atoms of the same element dont satisfy the octet rule, just enter the chemical symbol as many times as necessary. for example, if two oxygen atoms dont satisfy the octet rule, enter \o,o\.

Explanation:

Step1: Calculate valence - electrons for \(H_2C_2\)

Carbon has 4 valence electrons and hydrogen has 1 valence electron. For \(H_2C_2\), \(2\times1 + 2\times4=10\) for the neutral molecule, but the given structure has lone - pairs that make the count wrong. The correct structure of \(C_2H_2\) (acetylene) is \(H - C\equiv C - H\) with a total of \(2\times1+2\times4 = 10\) valence electrons. The given structure has extra non - bonding electrons, and the correct number of valence electrons for the neutral species is 10, but if we consider the way it is drawn with the given lone - pairs, the actual correct count for a proper Lewis structure of a neutral \(C_2H_2\) is 10 and the given structure has more than 10. In a proper Lewis structure of \(C_2H_2\) (acetylene), there are no non - bonding electrons on carbon atoms and the total valence electrons are \(2\times1+2\times4 = 10\). If we assume it is a non - standard form with non - bonding electrons shown, the correct count for a stable structure of \(C_2H_2\) is 10 and the given one has wrong count. For a more accurate count considering the structure as drawn, the correct number of valence electrons for a proper Lewis structure of the molecule related to the given structure is 12 (accounting for the non - bonding electrons in a proper way).

Step2: Calculate valence - electrons for \(NOCl\)

Nitrogen has 5 valence electrons, oxygen has 6 valence electrons, and chlorine has 7 valence electrons. So, \(5 + 6+7=18\) for the neutral \(NOCl\) molecule. The given structure has the wrong number of valence electrons. The correct number is \(5 + 6+7 = 24\) when we consider the proper distribution of electrons to satisfy the octet rule for all atoms.

Step3: Analyze \(HC\equiv C^-\)

Hydrogen has 1 valence electron, and each carbon has 4 valence electrons. The ion \(HC\equiv C^-\) has \(1+4 + 4+1=10\) valence electrons (the extra 1 comes from the negative charge). The given Lewis structure \([H - C\equiv C:]^-\) has the correct number of valence electrons and satisfies the octet rule for both carbon atoms (the triple bond between carbons and the single bond to hydrogen along with the lone pair on the terminal carbon and the negative charge account for all 10 valence electrons). So, this Lewis structure is reasonable.

Answer:

1. No, it has the wrong number of valence electrons. The correct number is: 12
2. No, it has the wrong number of valence electrons. The correct number is: 24
3. Yes.